About whether an impressive Hasseblad is needed in applications where results are similar to a D800 ...

For well-informed clients, no.

For poorly-informed clients (but with checkbooks), yes.

I guess some photographers get to a point where they turn down jobs because a client (aka boss) is poorly-informed about equipment.

Being right doesn't pay the rent unless you've reached the level of famous diva-tographer.

I imagine if the job called for some work that required an ISO higher than 200, the choice would be really simple. I was surprised at how noisy the Hassy was. Not even in the same class as my GH3, it seems. For that kind of money I'd expect better.

The new Hasseblad with the Sony CMOS sensor should be much better at higher ISOs